Some of the largest seabird colonies in the world can be found in Iceland. 25 seabird species are known to have nested in Iceland and at least 29 others have been sighted. Many other species that we usually associate with other ecosystems do in fact also rely on the ocean for part of the year.

The seabird community around Iceland is composed of relatively few but very abundant species. The most important group is the auks with 6 species, of which 4 are extremely abundant. Many bird species only stay around Iceland in winter to take advantage of the high summer productivity but overwinter in southern locations. The most famous example of this, as well as the most extreme, is the Arctic tern. It spends the summer in the Arctic and the winter in the Antarctic (of course it is summer there by then). Others such as the northern fulmar are resident in Icelandic waters all year round. There are also a few cases, such as little auks and some gull species, where the birds overwinter in Iceland but migrate further north during the summer to feed and nest.

Besides the classical seabirds described below, many other species benefit from the marine environment. Two species of divers (Gaviidae) and two species of phalaropes (Phalaropus spp.) are, for example, usually associated with freshwater lakes or wetlands but are actually only found on the ocean in the winter. Many species of wading birds (Charadriiformes) are also dependent on the seashore, the interface between sea and land. On the other hand, several species that we associate with the marine environment can, and often will, thrive on land. This is for example common among the gull species.

Fulmars and related birds (Procellariiformes)

The northernfulmar (Fulmaris glacialis) is, together with the puffin, the most abundant seabird around Iceland; the former with 1 to 2 million breeding pairs and the latter with 2 to 3 million. It might seem surprising that only one century ago the fulmar was not particularly abundant. This is probably because it is a surface feeding scavenger and has benefited enormously from the fisheries. Other related species nesting in Iceland are Manx shearwater (Puffinus puffinus), storm petrel (Hydrobates pelagicus), and Leach´s petrel (Oceanodroma leucorrhoa). These are quite common, but inconspicuous and not well known to the public because they are almost purely open ocean birds and therefore rarely seen. Albatrosses are in this group and have only been spotted a few times around Iceland. Fulmars are not hunted in Iceland but eggs and chicks were harvested in the past.

Gannets and cormorants (Pelecaniformes)

These are among the largest of the seabirds and therefore quite conspicuous. Gannets and cormorants are, however, quite different. Gannets (Sula bassana) are the largest seabirds around Iceland and are famous for their high velocity dives into the ocean to catch fish. Cormorants are clumsy flyers but among the best divers of all birds. Two species are found around Iceland, the great cormorant (Phalacrocorax carbo) and shag (P. aristotelix). Both are quite common. Gannets and cormorants have been hunted in Iceland throughout the centuries but adult gannets are now protected.

Ducks (Anseriformes)

Only one species of duck in Iceland is truly marine, the common eider (Somateria mollissima). It is very abundant and quite conspicuous as it lives exclusively in shallow marine waters. The numbers of eiders around Iceland are kept artificially high since the bird is semi-domesticated. Eiderdown harvesting has been economically quite important through the ages. The down is collected from the nests and in return farmers actively protect the nesting sites during the breeding period. Many other species of ducks feed on the seashore and in shallow coastal waters in winter.

Gulls (Lari)

Many species of gulls can be found around Iceland. Some, such as herring gulls (Larus argentatus) and great black-backed gulls (L. marinus) nest and live around Iceland the entire year. Others, such as Iceland gulls (L. glaucoides) and Glacous gulls (L. hyperboreus), mostly breed in the Arctic north of Iceland but visit Icelandic waters in the winter. Still others, like the lesser black-backed gulls (L. fuscus) and black headed gulls (L. ridibundus), nest in Iceland in summer, but usually migrate south to Europe or North America in winter. Looking from the seashore, one might think that some of these Larus species might be the most common Icelandic gulls, but that is not the case. By far the most common gull species is the blacked-legged kittiwake (Rissa tridactyla) which is more abundant than all the Larus species combined. However, it is the only gull species that is a true offshore bird and rarely seen close to land except during the breeding period. The kittiwake is well known to fishermen, as it is, with the fulmar, the most common scavenging bird around fishing boats. Other related species are the terns, of which only the Arctic tern (Sterna paradisea) breeds in Iceland, and two species of skuas, Arctic skua (Stercorarius parasiticus) and great skua (S. skua).

Auks (Alcidae)

Most seabirds nest in large colonies in cliffs or other isolated places. The auks are the archetypical of these birds. Huge colonies exist around Iceland with puffins (Fratercula arctica), Brunnich´s guillemots (Uria lomvia), common guillemots (Uria aalge) and razorbills (Alca torda). Little auks (Alle alle) are not rare in winter but probably do not breed in Iceland anymore, possibly due to the warming trend. Further north, closer to the high Arctic, they are the most abundant seabird species. Black guillemots (Cepphus grylle) also live around Iceland but are much rarer than the other species. Auks are considered a delicacy in Iceland and have been an important harvest around Iceland for centuries. Eggs and chicks are taken in nests and adults netted or, in recent times, shot at sea (never on the breeding sites). In most places around Iceland unofficial rules have been enforced in this hunt, only every other egg is taken or birds that are obviously bringing food to the chicks are left alone, so that these resources will not be depleted. This sensible practice, however, did not save the last great auk (Pinguinus impennis) on earth from being killed in Iceland in 1844.

Foraging by seabirds

Most seabirds feed on small fishes, cephalopods or crustaceans in the upper levels of the water column. Generally, the smaller the bird the smaller the prey: cormorants can, for example, feed on quite large fish, while the little auk mainly eats copepods. On the whole, the main fish prey is the capelin in north Icelandic waters and sandeels in south Icelandic waters. Although bird species might feed on similar prey they use quite different methods. Fulmars, kittiwakes and terns are poor divers but very good flyers. They skim the surface over vast distances in search of food on the surface. These have also been able to adapt well to scavenging from fisheries. Others, like the cormorants and the auks, are poor flyers but very good divers and can dive quite deep for prey. The main exception to this prey selection pattern is the eider. They forage in shallow waters for various benthic invertebrates.